Making random structures
[Option 1]
is to do it via displacement:
Here via shader displacement and a Musgave texture. This way it stays parametric. Works only with cycles in render view/render.






If you want it to be a solid mesh to further work on here is a tutorial how to do that: https://www.youtube.com/watch?v=McALCOr39rY  

[Option 2]
The other way would be from curves, but is not parametric.
Convert your pattern from an image to curve for expl. in illustrator,
then use these curves to build your mesh.
curve menue>extrude
then: convert to mesh from curves